Fixed capacitor



R- W. NEIBAUR FIXED CAPACITOR Nov. 10, 1964 Original Filed April 16,1957 7 A 7 \v 3 6 H M o Vvwv A (M 4 E 6, E B M E; M. 8 if INVENTORHODER/c/r w. NE/BA UR United States Patent 3,156,852 FIXED CAPACITORRoderick W. Neibaur, San Jose, Calif., assignor, by mesne assignments,to Jennings Radio Manufacturing (Iorpw ration, San Jose, Calif., acorporation of Delaware Continuation of application Ser. No. 653,111,Apr. 16,

1957. This application June 17, 1964, Ser. No. 375,851 4 Claims. (Cl.317-244) My invention relates to fixed capacitors, and particularly tovacuum type fixed capacitors. This application is a continuation of mycopending application Serial No. 653,111, filed April 16, 1957.

One of the objects of my invention is the provision of a vacuum typefixed capacitor of exceptionally small size.

Another object is the provision of a vacuum type fixed capacitor havingrelatively high voltage and current ratings in relation to its size.

Still another object is the provision of a small size vacuum fixedcapacitor possessing qualities of mechanical rigidity and electricalstability found ordinarily only in much larger implements.

Still another object is a small vacuum fixed capacitor having anassembly of parts particularly adapting it for low cost manufacture.

Other objects will be brought out in the following description of theinvention. I do not limit myself to the showing made by said descriptionand the drawings, since I may use variant forms of the invention withinthe scope of the appended claims.

Referring to the drawing:

The figure is a vertical half sectional view, enlarged approximatelyfour times actual size.

Broadly considered, the vacuum fixed capacitor of my invention comprisesan evacuated envelope formed by two aligned metallic end caps spacedapart and hermetically closing opposite ends of a hollow dielectricshell interposed between the caps. Within the envelope a plurality ofcylindrical condenser plates are rigidly mounted on each end cap toextend into the envelope in spaced interleaved relation. An inwardlyextending boss constituting an outwardly opening thimble integrallyformed in each end cap is filled with an integrally united hollowterminal plug, useful to connect the capacitor into a circuit.

In more specific terms, my fixed capacitor comprises an evacuatedenvelope symmetrical about a longitudinal axis and formed by a hollowcylindrical dielectric shell 2, closed at each opposite end by aninwardly opening copper end cap 3. Each of the end caps is cup-shaped toprovide a circular end plate 4, having a slightly flaring integralflange 6 extending from its outer periphery. The free end of the flangeis bonded hermetically to the associated end of the dielectric shell bythe conventional metal-to-glass seal 7. While glass has been shown inthe present embodiment, it is contemplated that other dielectricmaterial, such as ceramic, may be bonded to the metal end caps to formthe dielectric shell.

To provide convenient terminal means for connecting the capacitor into acircuit, each of the end caps is provided with a concentric, integral,inwardly extending, outwardly opening thimble 8, in which the terminalplug 9 is integrally brazed. The plug is hollow and preferably providedwith internal threads 12 by which a terminal lead (not shown) may bereleasably secured to the end cap.

To facilitate brazing the plug within the thimble, the plug is providedwith an annular groove 13 adjacent its inner end, within which thebrazing material may be placed prior to heating, and from which it willspread between the adjacent surfaces of plug and thimble to integrallyunite the parts.

The inwardly extending thimble and the peripheral flange 6 of each endcap thus define, with the plate 4 from which each is formed, an inwardlyopening annular channel within which are integrally brazed a pluralityof concentric cylindrical condenser plates 14.

The condenser plates fixed in each cap form a set or group which isarranged in spaced interleaved relationship with the plates fixed in thecap opposite. The two groups are identical except in diameter of theindividual plates, which vary by a fixed increment from the smallest orinnermost plate to the largest or outermost. The assembled plates of thesets form annular groups of slightly different overall diameters, butthe same length and the same radial thickness in both sets. Each of thecondenser plates at its fixed end is provided with a radially extendingflange 16 integrally united as by brazing to the plate 4, and eachplate, except the inner or smallest of each set, is also provided withan integral reentrant cylindrical flange 17, closely fitting andintegrally united with the next adjacent smaller plate.

A rigid, integral structure is thus formed, possessing the requisitestrength to withstand rough handling and electrically imposedvibrations. The coalesced character of the union between condenserplates and end caps also provides a minimum, direct and continuous pathfor the con duction of heat outwardly to the radiating surfaces of endcaps and dielectric shell. Evacuation of the capacitor envelope isaccomplished through the tubulation 18 in the dielectric shell.

As shown in the drawing, the condenser plates are closely spaced andextend into the envelope to a point within the annular channel of theopposite end cap. The plates are thus interleaved for a major portion oftheir length to provide a voltage rating of approximately 7.5 kilovoltspeak, and a current rating of 30 amperes R.M.S., in a capacitorapproximately 1% long and 1%" in diameter. Because of the readilysecured great accuracy of shape and assembly permitted by theinterfitting flange and mounting construction of the condenser plateends, and because of the substantial duplication of the end capassemblies, material savings in costs of manufacture are possiblewithout any sacrifice of high capacitance and high quality, each ofwhich usually make heavy demands on production costs.

I claim:

1. A vacuum fixed capacitor comprising an evacuated envelope includingaligned metallic end caps spaced apart and hermetically closing oppositeends of a dielectric shell interposed therebetween, each said end capincluding a centrally disposed inwardly extending integral boss, and aplurality of mutually reaching integrally united concentric cylindricalcondenser plates fixed in each end cap and interleaved with thecondenser plates fixed in the opposite end cap.

2. The combination according to claim 1, in which said envelope issymmetrical about a longitudinal axis and the integral boss is hollowand constitutes an outwardly opening thimble.

3. In a vacuum fixed capacitor, the combination comprising a pair ofmetallic end caps spaced apart, each end cap having a concentricinwardly extending boss and a flaring peripheral flange defining withsaid concentric boss an annular channel, and a plurality of integrallyunited concentric cylindrical condenser plates fixed to each end capwithin the channel and terminating in a plane perpendicular to the axisof the capacitor and adjacent to the inner end of the boss on the otherend cap.

4. A vacuum fixed capacitor comprising an evacuated envelope symmetricalabout a longitudinal axis and ineluding aligned metallic end caps spacedapart and hermetically closing oppesite ends of a dielectric shell interposed therebetween, each said end cap including a peripheral flangeand a concentric inwardly extending outwardly opening integral thimbleand with said, peripheral flange defining an annular channel, and aplurality of mutually reaching integrally united concentric cylindricalcondenser plates fixed to the end cap within each channel andinterleaved with the condenser plates fixed in the 0pposite channel,each condenser plate having a length such that each plate terminates ina free end lying Within the channel of the opposite end cap.

Smith 31726O Teare 317244 X Osterman 317-260 Jennings 317-244 Smith eta1 3l7-256 X Luft 317-245 FOREIGN PATENTS JOHN F. BURNS, PrimaryExaminer.

1. A VACUUM FIXES CAPACITOR COMPRISING AN EVACUATED ENVELOPE INCLUDINGALIGNED METALLIC END CAPS SPACED APART AND HERMETICALLY CLOSING OPPOSITEENDS OF A DIELECTRIC SHELL INTERPOSED THEREBETWEEN, EACH SAID END CAPINCLUDING A CENTRALLY DISPOSED INWARDLY EXTENDING INTEGRAL BOSS, AND APLURALITY OF MUTUALLY REACHING INTEGRALLY UNITED CONCENTRIC CYLINDRICALCONDENSER PLATES FIXED IN EACH END CAP AND INTERLEAVED WITH THECONDENSER PLATES FIXED IN THE OPPOSITE END CAP.